Like kinases, ligases are a ripe target area. The difference is that ligases generally are harder to inhibit. Rigel Inc. thinks it achieved proof of principle in the ubiquitin ligase field for cancer a few years back, and now has advanced a small molecule ubiquitin ligase program in the infectious disease space.

Both protein kinases and ubiquitin ligases have similar roles: they modify protein function. Kinases do so by adding phosphate to a given substrate, while ubiquitin ligases work by adding ubiquitin.